The present invention relates to nozzles for generating a twist in a fiber sliver in textile spinning machines. Air injection nozzles having lateral bores entering a central yarn passage tangentially to the central passage are known. EP-A 0321885 describes a false twist air nozzle with a cylindrical, central yarn passage and tangentially arranged air injection bores opening into the central passage. Also described is a feed duct whose inner diameter is less than that of the central yarn passage leaving an extension which projects into a certain length of the cylindrical passage. The precise manner in which the air injection bores open into the duct is regarded as unimportant, and not described. One disadvantage of such a twist nozzle is that the nozzle is comprised of two components in conjunction with the feed duct and therefore requires considerably more mechanical processing.
DE-A-26'05'942 discloses a central yarn passage having several tangential compressed air injection bores opening directly into a yarn passage without describing the manner of bore entry. WO-A-89/03440 shows a central yarn passage having air injection ports with diameters increasing toward the point of entry into a central yarn passage. L'Industrie Textile, No. 1125 (September 1982), page 726 shows an air jet nozzle having four air infeed bores entering tangentially into a central yarn passage at a certain angle of inclination.
In general, where compressed air bores have been provided in an air jet nozzles for false twisting a yarn, it has been assumed that the bores should enter the central yarn passage in a perfect tangential manner.